The more we learn about the almost successful effort to blow up a U.S.-bound airplane on Christmas Day, the more astonishing it becomes that terrorists have not succeeded in killing more Americans in the years since 9/11.

One could write books about all that went wrong leading up to the latest narrowly averted disaster. Clearly, throwing tens of billions of dollars at homeland security will not by itself do the job of preventing terrorism. What is missing from the system is practical thinking.

Until now, security has focused on keeping weapons off airplanes. It's time to widen the focus to people and keep terrorists out of airports. Otherwise, innocent travelers will face ever more irritating, time-consuming procedures, each designed to prevent the previous attack. It's time to allow security officials to think.

Only one country has learned how to protect travelers from murderers driven by extreme political and religious ideologies: Israel.

There is no guarantee that terrorists will never again achieve their aim of destroying lives at an Israeli airport or airline. Still, it is a fact that Israel has kept travelers safe for more than three decades. That is all the more remarkable because most terrorist attacks have been perpetrated by Muslim extremists, whose hatred burns hottest against Israelis and Jews.

On Christmas Day, the one measure that worked to prevent the Nigerian terrorist Umar Farouk Abdulmutallab from killing nearly 300 passengers was the quick reaction of alert passengers. All the other systems put in place by the professionals played out like an anything-but-funny comedy of errors.

Nobody, it seems, is thinking. How much more information did authorities need to prevent the Nigerian killer from coming to America with no luggage other than explosives in his underwear?

The United States knew a Nigerian man was ready to carry out an attack hatched in Yemen. Umar Farouk Abdulmutallab's father contacted the U.S. embassy in Nigeria and warned a CIA officer that his missing son, who had spent time in Yemen, had become radicalized. Abdulmutallab paid for his ticket in cash. His name was already on the Terrorist Identity watch list. British officials had him on their own list and banned him from entering their country. And yet, nobody stopped him.

Anyone who has traveled through the Tel Aviv airport has seen what intelligent security looks like. Granted, Israelis deal with a far smaller number of passengers than the United States, but the cost of ignoring their experience is simply unacceptable. Try tallying the cost of 9/11.

Israelis guard a perimeter of several miles around the airport and use high technology to find dangerous materials. But the most important tool in preventive security is an active human mind. The core of the process is a personal interview; well-trained officials look for suspicious behavior. All available information goes into making the decision about which individuals can fly. The process is cumbersome and sometimes awkward. But it works.

Immediately after the foiled bombing, U.S. officials issued new security guidelines, which they promptly rescinded. Until major changes come, one directive should go to all security personnel from embassies to airports: It is now permitted — make that encouraged — to think. Otherwise, the unbelievably lucky close call over Detroit will only serve as prelude to disaster.